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Increased left atrial pressure inhibits hypoxic pulmonary vasoconstriction
D De Cannière1, C Stefanidis, R Hallemans
1Laboratory of Cardiovascular and Respiratory Physiology, Erasme University Hospital, Brussels, Belgium.
Journal of Applied Physiology (Bethesda, Md. : 1985)
|April 1, 1994
Summary
Increased left atrial pressure (Pla) inhibits hypoxic pulmonary vasoconstriction in piglets. This finding suggests that higher normal left atrial pressure does not contribute to pulmonary arterial pressure during hypoxia or hyperoxia.
Area of Science:
- Physiology
- Pulmonary Circulation
- Cardiovascular Research
Background:
- Hypoxic pulmonary vasoconstriction (HPV) response varies across species.
- Previous studies in dogs showed inconsistent effects of elevated left atrial pressure (Pla) on HPV.
- Piglets exhibit a more pronounced HPV response compared to dogs.
Purpose of the Study:
- To investigate the effect of elevated left atrial pressure (Pla) on pulmonary arterial pressure (Ppa) and flow (Q) relationships during hypoxia and hyperoxia in piglets.
- To determine if increased Pla influences the hypoxic pulmonary vasoconstriction (HPV) response in piglets.
- To examine the relationship between Ppa and Pla at constant flow (Q) under varying oxygen conditions.
Main Methods:
- Seven anesthetized piglets were utilized.
- Balloon catheters were inserted into the inferior vena cava and left atrium to control flow (Q) and Pla, respectively.
- Animals were ventilated with either hyperoxia (FIO2 0.4) or hypoxia (FIO2 0.12).
- Pulmonary arterial pressure (Ppa)-flow (Q) relationships and Ppa-Pla relationships at fixed Q were analyzed.
Main Results:
- Hypoxia increased the slope of Ppa-Q plots but did not alter the extrapolated pressure intercept (Pi).
- Elevated Pla (8 to 17 mmHg) caused a parallel shift in Ppa-Q plots in hyperoxia but not in hypoxia.
- Increased Pla at constant Q led to a proportional increase in Ppa during hyperoxia, with no effect during hypoxia.
- The hypoxia-induced increase in Ppa was attenuated by elevated Pla across all studied flow levels.
Conclusions:
- In piglets, hypoxia increases the slope of Ppa-Q relationships without affecting Pi at a fixed Pla.
- Elevated left atrial pressure (Pla) inhibits hypoxic pulmonary vasoconstriction (HPV) in piglets.
- The results indicate that a closing pressure higher than normal Pla does not contribute to pulmonary arterial pressure in the porcine pulmonary circulation under hyperoxic or hypoxic conditions.